JPH03162010A - Gate driving circuit for static induction transistor - Google Patents

Abstract

PURPOSE:To attain high speed driving stably without destroying or burning a transistor(TR) by applying a bias voltage to the gate of an electrostatic induction TR via a diode so as to clamp the part of a driving signal. CONSTITUTION:A series circuit (clamp circuit) comprising a diode D1 and a capacitor C1 is connected between the gate and the source of an electrostatic induction TR Q1. Moreover, the gate of the electrostatic induction TR Q1 and a connecting point between switching TRs Q3, Q4 and the negative DC power supply -VG of a driving circuit 1 and a connecting point between the diode D1 and the capacitor C1 are connected respectively through coaxial cables 2, 3. Then part or all of the power supply voltage of the circuit 1 is applied to the gate of the electrostatic induction TR Q1 through the diode D1 and part of the driving signal is clamped to keep a prescribed voltage level. Thus, the TR is not burned or damaged even when the TR is driven at high speed and the TR is driven stably.

Description

[Detailed Description of the Invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to a gate drive circuit for driving a static induction transistor at high speed. b. Conventional technology A static induction transistor is a type of field effect transistor. This is a semiconductor device that is controlled by the voltage applied to the third electrode. especially,
The drain current of this type of transistor is non-saturated with respect to the voltage between the drain and source, and when the transistor is driven and controlled by the voltage from the gate, it exhibits triode characteristics.

Conventionally, as a method for driving this type of static induction transistor at high speed, there has been a driving circuit as shown in FIG. 5, for example. (For example, "Static Induction Transistor Handbook" Vol. 05. P published by Tohoku Metal Industry Co., Ltd.
35) In the same figure, Q is a static induction type transistor, E1 is its DC power supply, and R. is the load, l is the transistor Q. This is the drive circuit. The transistor Q2 and the resistor R of the drive circuit l are a circuit for driving the switching transistor (h, Q4) that prevents the emitter 7-tough flow circuit, and the high-speed pulse signal from the pulse generator PG is connected to the resistor R. . is applied to the negative side of the transistor Q2.Here, +V6, -V, are DC t sources of the drive circuit 1.

Generally, when the electrostatic induction transistor 01 is used as a power switching element, the drive circuit 1 and the transistor Q1 are connected by a cable (coaxial cable in the figure) 2 as shown in FIG.

C. Problems to be Solved by the Invention Although it is better for the cable 2 for the connection described above to be short, a certain length of cable is unavoidable when connecting multiple static induction transistors Q1 or when using them in parallel. 2 will be needed.

However, when the static induction transistor Q is switched at high speed using a cable 2 of a certain length as shown in FIG. 6, the gate-source voltage VCS of the transistor Q1 is as shown in FIG. It changes as shown by the solid line. What is problematic about the waveform in the same figure is the part shown in ■ and ■ among the changes in the gate-source voltages VC and S of the static induction transistor Q at the falling edge of the output pulse signal of the pulse generator PC. If the absolute value of the voltage at the part (■) is large, the absolute maximum rating value of the gate-source voltage VCS of the transistor Q1 will be exceeded, and the voltage of the transistor Q. damage. On the other hand, if the voltage at the part (■) increases, the electrostatic induction transistor Q will malfunction, and especially in the case of a bridge type inverter that uses multiple transistors 01, the transistors will turn on at the same time, causing a short circuit current. There was a problem with it flowing and burning out.

Therefore, driving the electrostatic induction type transistor at a higher speed increases the absolute value of the voltage in the part ``■'' shown in FIG. 3, and also increases the voltage in the part ``■''.
There was a problem that it became difficult to increase the speed.

The present invention has been made in view of the above-mentioned problems, and its purpose is to solve the above-mentioned problems, and even when driven at high speed, the electrostatic Si I
An object of the present invention is to provide a gate drive circuit for a transistor that can stably drive the transistor without damaging or burning out the transistor.

d. Means for Solving the Problems The principles of the present invention for achieving the above objects are as follows (1) and (2) in a gate drive circuit for a static induction transistor driven at high speed. It is.

(1) A negative bias voltage is applied to the gate side of the electrostatic induction transistor via a diode, and a part of the drive signal is clamped to enable high-speed driving of the transistor. do.

(2) A series circuit of a diode and a capacitor is inserted between the gate and source of the static induction transistor, and a part of the drive signal is clamped by connecting the power supply of the drive circuit to both ends of the capacitor. , is characterized in that the transistor can be driven at high speed.

e. Function: The gate drive circuit for a static induction transistor configured as described above applies part or all of the power supply voltage of the drive circuit to the gate side of the transistor through a diode, and receives one of the drive signals. ie, hold part of the drive signal at a predetermined voltage level. As a result, the change in the gate-source voltage VaS of the Hatake transistor is the seventh
As shown by the dotted line (■) in the figure, the gate-source voltage of the electrostatic induction transistor is stabilized, making it possible to drive the transistor at high speed.

f. EXAMPLES Hereinafter, preferred embodiments of the present invention will be described in detail by way of example based on the drawings.

FIG. 1 is a main circuit diagram of a gate drive circuit for a static induction transistor according to an embodiment of the present invention. In the figure,
Electrostatic induction type transistor. A diode D. is connected between the gate and source of D. and the capacitor C1 (so-called clamp circuit), and the switching transistor Q. , Q. and the gate of the electrostatic induction transistor Q1, and between the negative side of the DC power supply -■ of the drive circuit 1 and the diode D, and the capacitor C1.
are connected to the connection points via coaxial cables 2.3, respectively. In addition, in the same figure? The same members as in FIG. 5 are designated by the same reference numerals, and their explanations will be omitted.

By the way, before explaining the operation, the input equivalent circuit of the electrostatic induction transistor Q1 will be explained. Figure 2 (A)
is a symbolic diagram of the transistor Q, and FIG. 2(B) is its equivalent circuit, G is the gate, S is the source. D is the drain, C,, is the gate-source capacitance co is the gate-source capacitance,
The capacitance between the drains, DL, is the equivalent built-in diode of the transistor Q1. Then, the human capacitance Cin of the transistor Q, when energized, is expressed by the following equation.

C+-=Ccs+(IAv)XCco, where ^9 is the voltage amplification gain of the electrostatic induction transistor Q. In the above equation, (1-AV)XCGD is a component called the so-called mirror effect and has a considerably large value.

Therefore, if we look at the electrical equivalent circuit including the coaxial cable 2.3 in FIG. 1, it will be as shown in FIG. 3. In the figure, SWI
is the switching element of the switching transistor 0■0, LI+ t. , is the inductance of the cable 2.3.

In FIG. 3, the switching element is now connected. is connected to the DC power supply +vG of the drive circuit l, the inductance L
1 through human capacitance it c. - is charged to a positive voltage, turning on the electrostatic induction transistor Q. Input capacity fJCi. When the voltage increases and reaches the forward operating voltage of the built-in diode D, current flows through the diode D, and the voltage of the human power capacitor Ci++ is clamped.

Next, when the switching element S-1 is connected to the DC power supply VG, the electric charge charged in the human power capacitor Ci++ is discharged through the inductance, making the gate-source voltage VGS a negative voltage and causing electrostatic induction. type transistor g1
Turn off. The voltage of input capacitance Ci+n is the power supply - VG
When the voltage reaches VGS, the gate-source voltage VGS is clamped at the same voltage by the diode D, and the voltage R vc
The voltage will not drop below . Here, the capacitor CI is always charged to the voltage of the power supply -V, and the gate-source voltage is V. When clamped with diode D, it acts as a bypass capacitor to allow instantaneous current to flow.

? Since the conventional gate drive circuit does not have a clamp circuit consisting of the diode D1 and the capacitor CI, the switching element SW. is connected to a power supply of 1 V, the input voltage is 3
The charge charged in 1ci flows through the inductance and causes oscillation due to the time constant of the input capacitance Cin, and the gate-source voltage ν, S is the power supply 1ν. In some cases, the voltage drops below the voltage of the static induction type transistor. exceeds the permissible gate-source voltage VGS of the transistor Q.
1 will be damaged.

However, according to the circuit shown in FIG. 3 of this embodiment, the gate-source voltage VCS does not fall below the voltage of the power supply -v6. Furthermore, no vibration occurs when the input capacitance Cin is discharged. Since the capacitor C1 is always charged to the voltage of the power supply -VC, the switching element SW+ is charged to the voltage of the power supply -VC.
6, no current flows through the circuit including inductance L2, diode DI+, inductance L+, and switching element SW. Therefore, no load is placed on the switching element SW.

FIG. 4 shows another embodiment of the present invention, and is a main circuit diagram of a gate drive circuit for a static induction transistor used in a full bridge high frequency inverter. In the same figure, Q
．． ．． Q. , Q. , Q. are static induction type transistors, and as shown in transistor Q6, the same clamp circuit consisting of a diode D2 and a capacitor Ct is used between the gate and source of each transistor, and the drive circuit 1 and The transistor Q&t
The gates of - and -Q are connected by a cable 4.

The operation of this embodiment is similar to that of the previous embodiment, and it has been found that this embodiment, which requires cable connection, has the following advantages.

(1) Since high-speed pulse drive is possible using a cable, multiple electrostatic induction transistors can be connected in parallel. Therefore, it is possible to manufacture a large capacity inverter.

(2) High-speed pulse drive is possible without damaging the electrostatic induction transistor, improving reliability and reducing switching loss. For this reason,
Highly efficient inverters can be manufactured.

(3) Since the switching speed can be increased, higher frequency inverters can be manufactured. In the applicant, I
It has become possible to manufacture MHz band inverters. (4)
Since the drive circuit only needs to flow charging/discharging current during switching, the power consumption of the drive circuit can be reduced.

It should be noted that the technology of the present invention is not limited to the technology in the above-mentioned embodiments, and means of other modes that perform the same function may be used. , can be added. g. Effects of the Invention As is clear from the above explanation, according to the gate drive circuit of the present invention, a bias voltage is applied to the gate side of the static induction transistor via the diode, or the bias voltage is applied to the gate side of the static induction transistor. By inserting a series circuit of a diode and a capacitor between the gate and source and connecting the power supply of the drive circuit to both ends of the capacitor, a part of the drive signal is clamped. It is possible to stably drive the static 1t induction type transistor without damaging or burning it out.

[Brief explanation of the drawing]

Figure 1 is a main circuit diagram showing one embodiment of the gate drive circuit of the static induction transistor of the present invention, Figure 2 (^> is a symbol diagram of the transistor, and Figure 2 (B) is the equivalent of the transistor. Circuit diagram, FIG. 3 is an equivalent circuit diagram of FIG. 1, and FIG. 4 is a main circuit diagram of a gate drive circuit of a static induction transistor used in a full-bridge high-frequency inverter showing another embodiment of the present invention. , Fig. 5 is a drive circuit diagram of a conventional electrostatic induction type transistor, Fig. 6 is a drive circuit diagram of a conventionally put into practical use as shown in Fig. 5, and Fig. 7 is a diagram of a drive circuit from the pulse generator in Fig. 6. It is a gate-source voltage waveform diagram of an electrostatic induction transistor in response to a pulse signal. 1...Drive circuit, C., C1...Capacitor, D,, D1...Diode, Q,, Q.~ Q,...static induction type transistor, E
．． , Et, +V. , -ν6...DC power supply. M Engraving of drawings (A) (B) 0 lK Display of 2011 Patent Application No. 301441 Name of the invention Related to the case involving a person who corrects the gate drive circuit of a static induction transistor Electricity

Claims (1)

[Claims] 1) In a gate drive circuit for a static induction transistor driven at high speed, a negative bias voltage is applied to the gate side of the static induction transistor via a diode, and a drive signal is applied to the gate side of the static induction transistor. 1. A gate drive circuit for a static induction transistor, characterized in that a part of the transistor is clamped to enable high-speed driving of the transistor. 2) In a gate drive circuit for a static induction transistor driven at high speed, a series circuit of a diode and a capacitor is inserted between the gate and source of the static induction transistor, and the drive circuit is connected to both ends of the capacitor. 1. A gate drive circuit for a static induction transistor, characterized in that a part of a drive signal is clamped by connecting a power source to enable high-speed drive of the transistor.